Castro in an interview with CNN

From Havana Bureau Chief Lucia Newman

OPORTO, Portugal (CNN) -- Fidel Castro has admitted to sending spies to the United States to gather information about "terrorist activities" by anti-Castro political groups, but the Cuban leader denied there were any attempts to spy on the U.S. military.

In an exclusive interview to be broadcast Tuesday on CNN's WorldView, Castro said, "Yes, we have sometimes dispatched Cuban citizens to the United States to infiltrate counterrevolutionary organizations, to inform us about activities that are of great interest to us."

"I think we have the right to do this," he said. "The United States has spies in industrial quantities."

The comments were believed to be the first time the Cuban leader has made such an admission.

Ten alleged Cuban spies were arrested in Florida last month in what authorities say is the largest Cuban spy ring uncovered in the United States since Castro came to power in 1959.

They were charged with trying to penetrate U.S. military bases, infiltrate anti-Castro exile groups and manipulate U.S. media and political organizations.

Castro made his comments during an interview in Portugal, where he was attending the Ibero-American summit. He was responding to a question about the arrests, acknowledging that Cuba placed spies in the United States.

"What information in the United States is it that interests us? One bit of information exclusively -- one thing fundamentally -- and that is the information about the terrorist activities against Cuba. The information about sabotage plans," he said.

Castro, however, denied sending spies to collect information on the U.S. military.

"We aren't interested in strategic matters, nor are we interested in information about military bases," Castro said.

But he said movements of U.S. military near Cuba would be of interest if the moves "translate into an act of aggression against Cuba. But we know that at this time that is not the fundamental thinking of the U.S. government."

There was no immediate comment from the State Department late Monday.

Fernando Rojas, spokesman for the Cuban American National Foundation, an anti-Castro lobbying group based in Miami, said the interview with Castro was further evidence the Cuban leader continues to be a threat to U.S. national security.

"He's now admitting to the fact he's exporting violence here to the shores of the United States," Rojas said.

Three of the 10 arrested on espionage charges have pleaded guilty to being an agent of a foreign government without notifying the U.S. Attorney General. The charge is punishable by a maximum penalty of 10 years in federal prison and a $250,000 fine.